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  A reply on Talk: Hadyn Parry: Re-engineering mosquitos to fight disease

  Jan 8 2013: Long-lasting insecticide-impregnated bednets (LLINs) have been - and are - very effective. However only a single class of insecticide, pyrethroids, is suitable for use on bednets, so widespread use will almost inevitably lead to resistance. This is already being seen. The development of new, effective tools would allow multiple tools to be used in combination, thereby not only being more effective but reducing the selective advantage from resistance to any one intervention and hence prolonging the useful life of all. So even though bednets are good it would still be wise urgently to develop and deploy additional control methods.

• A reply on Talk: Hadyn Parry: Re-engineering mosquitos to fight disease

  Jan 8 2013: The idea is based on the radiation-based sterile insect methods pioneered by Knipling and Bushland in the 1950s - and still used today to control some agricultural pests. Modern genetics allows various enhancements and hence the effective application of this approach to mosquitoes and public health.

• A reply on Talk: Hadyn Parry: Re-engineering mosquitos to fight disease

  Jan 5 2013: Repeated releases over a period of time would be required for the reason Joe suggests. At the outset, some females mate the steriles but some mate the wild males (depending on how many there are of each type, but there will always be some fraction mating the wild type). So in the next generation there will be fewer wild mosquitoes, but not none. However, if you continue to release the steriles, let's say at the same rate as previously, more wild females will mate steriles. But it's better than that - because there are fewer wild mosquitoes than at the outset, the ratio of sterile males to wild males is higher and so a higher proportion of the wild females will mate sterile males and the method becomes even more effective than it was at the outset. Of course is you stop releasing prior to elimination the target population will eventually recover back to its original level.
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  A reply on Conversation: Is the total eradication of mosquitoes a true solution?

  Jan 5 2013: For container breeders like Aedes aegypti (the key vector of dengue) the problem with larviciding is finding the breeding sites. Bacillus thuringiensis israelensis works well, as do various chemicals - but only if you can get them into the breeding sites, which are essentially any small water-filled container - bucket, blocked rainwater gutter, used tyres, etc. There are so many of these in any urban environment that it is near-impossible in practice to find and treat enough of them. A key feature of engineered sterile males is that they will actively seek out the wild females over a significant area and thereby solve this searh problem. I agree that the situation will vary from species to species; for some mosquitoes breeding in larger bodies of water such as Aedes taeniorhynchus use of larvicides seems more effective.
• +2

  A reply on Conversation: Is the total eradication of mosquitoes a true solution?

  Jan 5 2013: Any intervention (chemicals, engineered sterile males, whatever) should be analysed for potential risk to the environment and human health on a case by case basis. However, as a general point Jaroslaw's "it's an invading species" is a good one - one would not expect a recently arrived species to be a key part of a native ecosystem. In general, mosquitoes are not keystone species even where they are native. A commentary in Nature in 2010 suggest that the (hypothetical) elimination of all mosquitoes would have minimal effect
  http://www.nature.com/news/2010/100721/full/466432a.html
  even suggested role as pollinators seems minimal
  http://www.nature.com/nature/journal/v467/n7311/full/467027d.html
  However one feature of the use of engineered sterile males is that they are extremely species-specific; this would not be the elimination of 'mosquitoes' but of 'one species of mosquito in the area of the control programme'. There are about 3,500 named species of mosquito. Also, as other contributors have noted, one could suppress but not eliminate if that were thought desirable.

• A comment on Talk: Hadyn Parry: Re-engineering mosquitos to fight disease

  Jan 5 2013: Dustin - such approaches have been suggested and indeed are being developed, but no working prototypes yet. Invasive genetic systems such as that may be seen as more risky or controversial as there is at best limited ability to undo a release. This contrasts with self-limiting systems such as the 'sterile male' approach Oxitec is developing. On the other hand deployment of a more invasive system may be cheaper, as you indicate.